ABSTRACT This proposal responds to the NIDCR Behavioral and Social Intervention Clinical Trial Planning & Implementation Cooperative Agreement (UG3/UH3). Our goal is to clinically evaluate the effects of a school-based behavioral intervention to reduce the risk of dental caries in a cohort of kindergarten through 2nd grade (K-2) children. Coordinated Approach to Child Health (CATCH) is an evidence-based coordinated school health program, and has undergone several cluster-randomized controlled trials (CRCT) demonstrating sustainable long-term effectiveness in improving eating and physical activity behaviors, and reductions in obesity prevalence among low-income, diverse children. As part of our recent 12-month R34 grant (R34DE026245), we integrated oral health lessons and activities into the existing K-2 CATCH program. The new program, called CATCH Healthy Smiles, was successfully tested for feasibility with K, 1st and 2nd grade children in two low income Houston elementary schools. Of the 113 children with dental assessments, 54% of children in Kindergarten, 62% in grade 1 and 73% in grade 2 had caries experience defined by any untreated caries or at least one filled deciduous or permanent teeth. These results, and those of prior studies, warrant the need for evidence-based school health curricula for oral health promotion. Our primary aims are: 1) In the UG3 one-year planning period (2019-2020), our primary aim is to finalize measurement protocols, study databases, CATCH Healthy Smiles intervention content and delivery framework, school and staff training, and recruit schools for a 26 school cluster-RCT (CRCT). 2) In Years 2-6 (UH3, 2020-2025), our primary aim is to conduct a school-based CRCT to determine the efficacy of CATCH Healthy Smiles in reducing the incidence and progression of dental caries as measured at the tooth (d2,3mft/D2,3MFT) and tooth surface level (d2,3mfs/D2,3MFS) among children starting in kindergarten and following through 2nd grade enrolled across 26 schools serving low-income, ethnically-diverse children. We hypothesize that, at 3-year follow up (end of 2nd grade), as compared to children in the control schools (n=13 schools; 533 children), those in the intervention schools receiving CATCH Health Smiles (n=13 schools; 533 children) will demonstrate significantly reduced incidence and progression of dental caries. Process evaluation data will be collected throughout to monitor intervention dosage, reach and fidelity. Our secondary aims are, 1) to quantify the impact of CATCH Healthy Smiles on child behavioral, psychosocial and environmental outcomes, including child oral health behaviors, diet, and school nutrition environment, and 2) to examine the extent to which these child behavioral, psychosocial and environmental factors (tooth brushing, diet, oral health related quality of life) mediate the intervention effects on child caries risk. The suite of CATCH pre-K to high school programs are licensed by UTHealth to a public charity, the CATCH Global Foundation. This project is significant because if found to be effective, a platform for scalability, sustainability and dissemination of CATCH already exists, and opens a new line of research in school oral health.